Using Multilink PPP over ATM Links

This module contains conceptual information and configuration tasks for using Multilink PPP over ATM links. Multilink PPP is a method that is used to reduce latency and jitter for real-time traffic.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the "Feature Information for Using Multilink PPP over ATM Links" section.

Use Cisco Feature Navigator to find information about platform support and Cisco IOS and Catalyst OS software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Prerequisites for Using Multilink PPP over ATM Links

•Multilink PPP uses first-in first-out (FIFO) queueing for queueing and interleaving packets. Other queueing mechanisms such as low latency queueing (LLQ), weighted fair queueing (WFQ), and class-based weighted fair queueing (CBWFQ) can be used. If you want to use one of these alternative mechanisms, enable it before configuring Multilink.

Restrictions for Using Multilink PPP over ATM Links

•Only Voice over IP (VoIP) is supported; Voice over ATM is not supported.

Information About Using Multilink PPP over ATM Links

MQC and Multilink PPP over ATM Links

Before using Multilink PPP over ATM links, a policy map must be created. (See the "Prerequisites" section.) Policy maps are created using the Modular Quality of Service (QoS) Command-Line Interface (CLI) (MQC).

Virtual Template Interfaces

A virtual template interface is a logical interface that is configured with generic configuration information for a specific purpose or a configuration common to specific users, plus router-dependent information. The template takes the form of a list of Cisco IOS interface commands that are applied to virtual access interfaces, as needed.

Multilink Group Interfaces

A multilink group interface is a collection of interfaces that are bundled together in the multilink PPP configuration. With a multilink group interface, you can bundle interfaces into logical multilink groups.

How to Configure Multilink PPP over ATM Links

Note While the first two procedures are listed as optional, you must choose one or the other according to the Cisco router that you are using in your network.

Prerequisites

Before proceeding with this task, you must create a policy map. The policy map contains the configuration parameters used to apply a specific QoS feature, such as distributed LLQ (dLLQ), to the network traffic.

SUMMARY STEPS

1. enable

2. configureterminal

3. interface virtual-templatenumber

4. bandwidthkbps

5. ip address ip-addressmask [secondary]

6. service-policyoutputpolicy-map-name

7. service-policyinputpolicy-map-name

8. ppp multilink

9. ppp multilink fragment delaymilliseconds [microseconds]

10. ppp multilink interleave

11. end

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2

configureterminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

interface virtual-templatenumber

Example:

Router(config)# interface virtual-template 4

Creates a virtual template and enters interface configuration mode.

•Enter the virtual template number.

Step 4

bandwidthkbps

Example:

Router(config-if)# bandwidth 32

Sets the bandwidth value for an interface.

•Enter the bandwidth value in kilobits per second.

Step 5

ip address ip-addressmask [secondary]

Example:

Router(config-if)# ip address 10.10.100.1
255.255.255.0

Sets a primary IP address for an interface. This command can also set the optional secondary IP address for an interface.

Prerequisites

Before proceeding with this task, you must create a policy map. The policy map contains the configuration parameters used to apply a specific QoS feature, such as distributed LLQ (dLLQ), to the network traffic.

SUMMARY STEPS

1. enable

2. configureterminal

3. interface multilinkmultilink-bundle-number

4. ip address ip-addressmask [secondary]

5. service-policyoutputpolicy-map-name

6. service-policyinputpolicy-map-name

7. ppp multilink fragment delaymilliseconds [microseconds]

8. ppp multilink interleave

9. ppp multilink multiclass

10. end

DETAILED STEPS

Command or Action

Purpose

Step 1

enable

Example:

Router> enable

Enables privileged EXEC mode.

•Enter your password if prompted.

Step 2

configureterminal

Example:

Router# configure terminal

Enters global configuration mode.

Step 3

interface multilinkmultilink-bundle-number

Example:

Router(config)# interface multilink 1

Creates a multilink bundle and enters interface configuration mode.

•Enter the multilink bundle number.

Step 4

ip address ip-addressmask [secondary]

Example:

Router(config-if)# ip address 10.10.100.1
255.255.255.0

Sets a primary IP address for an interface. This command can also set the optional secondary IP address for an interface.

What to Do Next

After configuring Multilink PPP over ATM links on a multilink group interface, the next step is to associate the virtual template interface with the multilink group by completing the steps in the following section.

The following is an example of configuring Multilink PPP over ATM links on a virtual template interface:

Router> enable

Router# configure terminal

Router(config)# interface virtual-template 4

Router(config-if)# bandwidth 32

Router(config-if)# ip address 10.10.100.1 255.255.255.0

Router(config-if)# service-policy output policy1

Router(config-if)# service-policy input policy1

Router(config-if)# ppp multilink

Router(config-if)# ppp multilink fragment delay 20

Router(config-if)# ppp multilink interleave

Router(config-if)# end

Example: Configuring Multilink PPP over ATM Links on a Multilink Group Interface

The following is an example of configuring Multilink PPP over ATM links on a multilink group interface:

Router> enable

Router# configure terminal

Router(config)# interface multilink 1

Router(config-if)# ip address 10.10.100.1 255.255.255.0

Router(config-if)# service-policy output policy1

Router(config-if)# service-policy input policy1

Router(config-if)# ppp multilink fragment delay 20

Router(config-if)# ppp multilink interleave

Router(config-if)# ppp multilink multiclass

Router(config-if)# end

Example: Associating the Virtual Template Interface with the Multilink Group

The following is an example of associating the virtual template interface with the multilink group:

Router> enable

Router# configure terminal

Router(config)# interface virtual-template 2

Router(config-if)# no ip address

Router(config-if)# ppp multilink group 1

Router(config-if)# end

Example: Associating the Virtual Template Interface with an ATM PVC

The following is an example of associating the virtual template interface with an ATM PVC:

Router> enable

Router# configure terminal

Router(config)# interface atm2/0/0

Router(config-if)# pvc cisco 0/16

Router(config-if-atm-vc)# abr 100 80

Router(config-if-atm-vc)# protocol ppp virtual-template 2

Router(config-if-atm-vc)# end

Example: Verifying the Multilink PPP over ATM Links Configuration

The following is an example of the show ppp multilink command output. In this example, one multilink bundle called 7206-2 is on the system. This bundle has two member links: one active link and one inactive link.

RFCs

RFC

Title

RFC 1990

The PPP Multilink Protocol (MP)

RFC 2686

Multiclass Extension to Multilink PPP (MCML)

Technical Assistance

Description

Link

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Feature Information for Using Multilink PPP over ATM Links

Table 1 lists the features in this module and provides links to specific configuration information.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS and Catalyst OS software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 1 lists only the Cisco IOS software release that introduced support for a given feature in a given Cisco IOS software release train. Unless noted otherwise, subsequent releases of that Cisco IOS software release train also support that feature..

Table 1 Feature Information for Using Multilink PPP over ATM Links

Feature Name

Releases

Feature Information

Distributed Link Fragmentation and Interleaving for Frame Relay and ATM Interfaces on Cisco 7500 Series Routers

The following commands were introduced or modified: ppp multilink group

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